Domestic water wells in Eastern Ontario were identified in potentially vulnerable fractured and karst bedrock aquifers using geologic and geochemical data. A novel methodology is presented that evaluates ¹³⁷Cs and ²¹⁰Pbₑₓ as local indicators of groundwater vulnerability. The method is designed to determine the vulnerability of a specific well. Suspended sediment samples and well-bottom sediment samples were collected from both potentially vulnerable and non-vulnerable wells. Surface soil samples were also collected from West Rural Ottawa and the Township of Alfred & Plantagenet in Ontario, Canada. Gamma spectroscopy was used to analyze the samples and quantify the presence of the radionuclides in cps and cps/g. The spectral data indicate no significant difference in the activities of ²¹⁰Pbₑₓ among samples, but a significant difference in the activities of ¹³⁷Cs was observed between surface soil samples and well-bottom sediment samples collected from vulnerable wells. The data suggest that ²¹⁰Pbₑₓ does not act as a good indicator of vulnerable aquifers because of its geogenic origin. The anthropogenic origin of ¹³⁷Cs precludes this issue, and while ¹³⁷Cs was detected in measurable quantities at the surface, its use as an indicator of vulnerable aquifers is limited by hydrologic and geologic controls that prevent infiltration in vulnerable terrains.

The favoured option for disposal of low and intermediate level radioactive waste is burial deep underground. In the safety assessment of deep disposal facilities a possibility which has to be considered is the eventual penetration of the engineered and natural barriers by ground water. Unfortunately humic and fulvic acids, present in most natural waters, can combine with radionuclides to produce metal complexes which are potentially more mobile in the environment than the original radionuclides from which they are formed. Migration of such complexes via groundwater and/or subsequently surface water routes could result in accelerated release of radionuclides to the biosphere. Quantitative knowledge of the extent of possible metal humate and fulvate interactions is therefore of considerable importance. In this study the complexation of Ni, Eu and Ce by humic and fulvic acids present in both ground and surface waters has been investigated. In most studies, to simplify the chemistry involved, humics and fulvics are separated from the water in which they occur before determination of their complexation properties. However, the severe conditions employed in the extraction process could conceivably alter the very properties to be measured. Accordingly the complexation properties of humics and fulvics present in a surface water have been studied both before and after extraction. The major part of this study was undertaken using a High Performance Size Exclusion Chromatographic technique especially developed to facilitate determinations on nonextracted materials. A fluorescence technique was also investigated as a more rapid alternative but was found to be of limited applicability. Complexation parameters were derived using a strong and weak site model. The effects of side reactions, ionic strength, pH, ligand type and nature of the cation were taken into account. With respect to measured stability constants, no major differences between ground and surface waters or extracted and non extracted materials were found. However, measured capacities of humics and fulvics for metals showed some variation according to the nature of the material and the system.

La compréhension des mécanismes de transport et du comportement des radionucléides dans la biogéosphère sont nécessaires à l’évaluation des risques sanitaires et environnementaux de l’industrie nucléaire. Ces mécanismes sont contrôlés par la spéciation des radioéléments, c’est-à-dire leur répartition entre leurs différentes formes physico-chimiques dans l’environnement. Dans cette optique, cette thèse traite de la spéciation de l’uranium en milieu naturel. La biogéochimie de l’uranium a fait l’objet d’une synthèse bibliographique détaillée, qui a permis de restreindre le sujet à la complexation de l’uranium par l’acide oxalique, un acide organique hydrophile fréquemment rencontré dans les sols et doté de bonnes propriétés de complexation. L’établissement de diagrammes de spéciation à partir des constantes de complexation de la littérature a permis de définir les conditions analytiques de formation des complexes. Le choix de la technique analytique s’est porté sur le couplage d’une technique séparative (chromatographie liquide LC ou électrophorèse capillaire EC) à la spectrométrie de masse (ICPMS). La présence des complexes étudiés dans les échantillons synthétiques a été vérifiée par spectrophotométrie UV/visible. Les analyses menées par LC-ICPMS ont prouvé la labilité des complexes uranyle-acides organiques, c’est-à-dire leur propension à se dissocier pendant l’analyse, ce qui empêche une détermination fiable de la spéciation de l’uranium. En revanche, l’étude des complexes labiles d’un système métal-ligand par ECICPMS a été rendue possible par l’emploi de la méthode d’affinité, permettant de déterminer les constantes de complexations et les mobilités électrophorétiques. Cette thèse a permis de comparer les différentes méthodes de traitement mathématique de l’isotherme de complexation et de prendre en compte la force ionique et la concentration réelle du ligand. La méthode d’affinité a été employée avec succès sur les systèmes lanthane-oxalate, pris comme modèle, et uranyle-oxalate. Les résultats obtenus ont été validés sur un système naturel (site du Bouchet). Ceci montre l’apport de la méthode mise au point dans la modélisation de la spéciation de l’uranium. / To understand the transport mechanisms and the radionuclides behaviour in the biogeosphere is necessary to evaluate healthy and environmental risks of nuclear industry. These mechanisms are monitored by radioelements speciation, namely the distribution between their different physico-chemical forms in the environment. From this perspective, this PhD thesis deals with uranium speciation in a natural background. A detailed summary of uranium biogeochemistry has been written, which enables to restrict the PhD issue to uranium complexation with oxalic acid, a hydrophilic organic acid with good binding properties, ubiquitous in soil waters. Analytical conditions have been established by means of speciation diagrams. The speciation diagrams building by means of literature stability constants has allowed to define the analytical conditions of complex formation. The chosen analytical technique is the hyphenation of a separative technique (liquid chromatography LC or capillary electrophoresis CE) with mass spectrometry (ICPMS). The studied complexes presence in the synthetic samples has been confirmed with UV/visible spectrophotometry. LC-ICPMS analyses have proved the lability of the uranyl-organic acid complexes, namely their tendency to dissociate during analysis, which prevents from studying uranium speciation. CE-ICPMS study of labile complexes from a metal-ligand system has been made possible by employing affinity capillary electrophoresis, which enables to determine stability constants and electrophoretic mobilities. This PhD thesis has allowed to compare the different mathematical treatments of binding isotherm and to take into account ionic strength and real ligand concentration. Affinity CE has been applied successfully to lanthanum-oxalate (model system) and uranium-oxalate systems. The obtained results have been applied to a real system (situated in Le Bouchet). This shows the contribution of the developed method to the modelling of uranium speciation.

O presente trabalho descreve a metodologia para a padronização dos radionuclídeos 111In e 18F e a determinação dos Coeficientes de Conversão Interna do 111In em Sistema de Coincidência por Software (SCS). O 111In decai com uma meia-vida de 2,8 dias por processo de captura eletrônica seguido por emissão de raios gama concorrendo com os elétrons da conversão interna. O 18F é um emissor de pósitrons de meia-vida curta (1,8 h), usado em Medicina Nuclear. As soluções radioativas usadas neste trabalho foram fornecidas pelo Centro de Radiofarmácia do IPEN e as massas determinadas pela técnica do picnômetro. As medidas foram feitas utilizando o Sistema de Coincidência 4πβ-γ constituído por um contador proporcional de geometria 4π a gás fluente e um semicondutor HPGe, acoplado a este sistema foi utilizado um sistema digital denominado de SCS com vantagem de obtenção da curva de extrapolação em uma única medida. A atividade do 111In foi determinada pela técnica de extrapolação linear da eficiência do contador proporcional usando absorvedores externos em ambos os lados das fontes. Os valores dos Coeficientes de Conversão Interna Total foram determinados selecionando duas janelas de raios gama (175 keV e 245 keV). A atividade do 18F foi determinada pela técnica de extrapolação linear da eficiência do contador proporcional utilizando a discriminação eletrônica. O código de simulação Monte Carlo ESQUEMA versão 9 foi usado para simular a extrapolação da curva da eficiência do 18F, considerando as características do esquema de desintegração e todos os detalhes geométricos do sistema de detecção. / This paper describes the methodology for standardization of radionuclides 111In and 18F and the determination of Total Internal Coefficients of 111In by means of a software coincidence system (SCS). The 111In decays with a half-life of 2.8 days by the electron capture process followed by gamma rays emission competing with internal conversion electrons. The 18F is a positron emitter with a short halflife (1.8 h), used in Nuclear Medicine. The radioactive solutions were provided by the Center for Radiopharmacy IPEN and the masses determined by pycnometer technique. The measurements were made using a Coincidence System 4πβ-γ consisting of a proportional counter in 4π geometry fluent gas and a HPGe semiconductor, coupled to the system was used a digital system called SCS with the advantage of obtaining the extrapolation curve in a single measurement. The activity of 111In was achieved by means of the linear extrapolation technique of the proportional counter efficiency using external absorbers on both sides of the sources. The values of the Total Internal Coefficients were determined selecting the two windows of gamma rays (175 keV and 245 keV). The activity of 18F was determined by means of the linear extrapolation, using electronic discrimination. The Monte Carlo simulation code ESQUEMA version 9 was used to simulate the efficiency curve extrapolation of the 18F, considering the characteristics of the system, the decay scheme of disintegration and all geometric details of the detection system.

O presente trabalho descreve a metodologia para a padronização dos radionuclídeos 111In e 18F e a determinação dos Coeficientes de Conversão Interna do 111In em Sistema de Coincidência por Software (SCS). O 111In decai com uma meia-vida de 2,8 dias por processo de captura eletrônica seguido por emissão de raios gama concorrendo com os elétrons da conversão interna. O 18F é um emissor de pósitrons de meia-vida curta (1,8 h), usado em Medicina Nuclear. As soluções radioativas usadas neste trabalho foram fornecidas pelo Centro de Radiofarmácia do IPEN e as massas determinadas pela técnica do picnômetro. As medidas foram feitas utilizando o Sistema de Coincidência 4πβ-γ constituído por um contador proporcional de geometria 4π a gás fluente e um semicondutor HPGe, acoplado a este sistema foi utilizado um sistema digital denominado de SCS com vantagem de obtenção da curva de extrapolação em uma única medida. A atividade do 111In foi determinada pela técnica de extrapolação linear da eficiência do contador proporcional usando absorvedores externos em ambos os lados das fontes. Os valores dos Coeficientes de Conversão Interna Total foram determinados selecionando duas janelas de raios gama (175 keV e 245 keV). A atividade do 18F foi determinada pela técnica de extrapolação linear da eficiência do contador proporcional utilizando a discriminação eletrônica. O código de simulação Monte Carlo ESQUEMA versão 9 foi usado para simular a extrapolação da curva da eficiência do 18F, considerando as características do esquema de desintegração e todos os detalhes geométricos do sistema de detecção. / This paper describes the methodology for standardization of radionuclides 111In and 18F and the determination of Total Internal Coefficients of 111In by means of a software coincidence system (SCS). The 111In decays with a half-life of 2.8 days by the electron capture process followed by gamma rays emission competing with internal conversion electrons. The 18F is a positron emitter with a short halflife (1.8 h), used in Nuclear Medicine. The radioactive solutions were provided by the Center for Radiopharmacy IPEN and the masses determined by pycnometer technique. The measurements were made using a Coincidence System 4πβ-γ consisting of a proportional counter in 4π geometry fluent gas and a HPGe semiconductor, coupled to the system was used a digital system called SCS with the advantage of obtaining the extrapolation curve in a single measurement. The activity of 111In was achieved by means of the linear extrapolation technique of the proportional counter efficiency using external absorbers on both sides of the sources. The values of the Total Internal Coefficients were determined selecting the two windows of gamma rays (175 keV and 245 keV). The activity of 18F was determined by means of the linear extrapolation, using electronic discrimination. The Monte Carlo simulation code ESQUEMA version 9 was used to simulate the efficiency curve extrapolation of the 18F, considering the characteristics of the system, the decay scheme of disintegration and all geometric details of the detection system.

Philosophiae Doctor - PhD / Coal fly ash has been studied extensively to understand the environmental impacts associated with its disposal, management and reuse. Although several beneficiation processes have been proposed, there has been little or no emphasis on the environmental safety of such processes, products and wastes. Elemental analysis has revealed that toxic elements and radionuclides are present in coal fly ash. Rare earth elements (REE) such as La, Ce and Y are also present in significant amounts in coal fly ash. The aims of this study were to determine the total elemental composition of coal fly ash using different analytical techniques; to validate the application potentials of fly ash beneficiation processes in terms of their environmental safety; and to valorise coal fly ash with a view of recovering REE either by concentrating or leaching the REE in the coal fly ash, products or waste from the beneficiation processes. The beneficiation processes studied were treatment of acid mine drainage (AMD) with fly ash; and the synthesis of geopolymer from fly ash. The fresh fly ash sample used in this study was collected directly from the hoppers at Matla power station and the AMD sample was collected from Carletonville goldmine. A total of 54 major, trace and REE were accurately determined in the ash using different analytical techniques. It was shown that the elemental content of Matla fly ash was of the same order as the SRM NIST coal fly ash 1633b. The comparative study of the four analytical techniques established that ENAA can accurately determine the major, minor and trace elements; that XRF is best suited for the determination of the major and minor elements, whilst the LA ICP-MS is reliable for trace elements determination. The solid residue (AMD/FA) resulting from the AMD interaction with fly ash was characterized with fly ash and the results compared. The results revealed that the amounts of La (141.09 ± 3.85 mg/kg), Ce (27.45 ± 2.04 mg/kg), and Nd (63.73 ± 0.05 mg/kg) in AMD/FA residue was considerably higher than their average abundance in the earth crust that varies from 66 mg/kg in Ce and 40 mg/kg in Nd to 35 mg/kg in La. The results also showed that the AMD/FA residue contained As (11.39 ± 1.21 mg/kg), Cd (3.77 ± 0.02 mg/kg), Cr (72.43 ± 1.27 mg/kg), Hg (10.50 ± 0.85 mg/kg), Ni (124.15 ± 1.6 mg/kg) and Pb (22.46 ± 1.43 mg/kg) which are potentially harmful if leached in to the environment in excessive amounts.

O Complexo Estuarino-Lagunar de Cananéia-Iguape, localizado no sul do Estado de São Paulo, Brasil, é uma área protegida reconhecida pela UNESCO como parte da Reserva da Biosfera, devido à sua importância como um ecossistema natural. Esta região sofreu mudanças importantes devido à abertura do Canal Valo Grande, ligando o rio Ribeira de Iguape ao Complexo, ocasionando a entrada de contaminantes no ecossistema. Para aprofundar os estudos deste ecossistema foi aprovado um Projeto de Pesquisa \"Estudo ambiental de sistemas costeiros expostos a importantes ações antrópicas na região sudeste por meio de ferramentas biogeoquímicas\". Este projeto teve como objetivo utilizar ferramentas biogeoquímicas no estudo de sistemas costeiros sujeitos a importantes influências antrópicas provenientes de ocupação do solo para fins de urbanização, agricultura, atividades industriais, reforma/instalação de estruturas portuárias e de exploração da plataforma costeira, sem deixar distante, as recomendações das ações de preservação e manejo que se fazem necessárias nas áreas costeiras. Dentro do escopo deste Projeto, o presente trabalho objetivou determinar a concentração dos radionuclídeos naturais Ra-226, Pb-210, Ra-228, K-40 e artificial Cs-137 em 34 amostras de sedimentos de superfície coletadas no Complexo Estuarino-Lagunar de Cananéia-Iguape. As amostras foram medidas por espectrometria gama, utilizando um detector Germanio Hiperpuro-HPGe. Os valores de concentração média obtidos nos sedimentos de superfície para o Ra-226 foi de 14,2 &plusmn; 8,7 Bq kg-1; para o Pb-210 foi de 31,1 &plusmn; 30,4 Bq kg-1; para Ra-228 de 19,2 &plusmn; 14,9 Bq kg-1 e para o K-40 318 &plusmn; 119 Bq kg-1. Os resultados obtidos indicaram que não há contaminação antropogênica e que esses valores podem ser considerados como níveis basais da região. Entretanto, os resultados obtidos para o desvio padrão relativo apresentaram valores altos, indicando grande dispersão dos resultados em torno do valor médio. Essa grande dispersão decorre principalmente das características físicas e químicas dos vários ecossistemas aonde foram amostrados os sedimentos. A Análise de Componentes Principais obtidos através da matriz de correlação de Pearson mostrou que em grande parte dos pontos amostrais, os radionuclídeos estudados estão presentes predominantemente na porção argila + silte e agregados à matéria orgânica. Dentro deste conjunto de pontos amostrais, foi possível evidenciar três pontos outliers, o ponto amostral MY3 que apresenta correlação mais positiva com as variáveis concentração de Ra-226 e Ra-228 e os pontos amostrais Pedra do Tombo e R6 que apresentaram maior correlação com a fração argila + silte e matéria orgânica. Já os demais pontos amostrais apresentaram correlação positiva com a variável areia, o que indica um padrão hidrodinâmico fortemente influenciado pelas correntes geradas pelas oscilações das marés e pela salinidade da água nesses locais. As maiores concentrações dos radionuclídeos no ponto amostral Pedra do Tombo, são devidas ao fato desse ponto apresentar altos teores de sedimentos pelíticos, alternância no fluxo de energia, ocorrendo alterações no sentido e intensidade do fluxo de água, permitindo a deposição dos sedimentos finos. Além do mais, esse local apresenta um afunilamento, que dificulta a passagem das frações finas que acabam se acumulando, facilitando a deposição dos radionuclídeos. Os resultados obtidos para o Cs-137 variaram entre <0,5 e 3,2 Bq kg-1. Dos resultados obtidos para a concentração do Cs-137 nas 34 amostras analisadas, 93% se encontram abaixo da concentração mínima detectável. A análise estatística dos resultados obtidos para o Cs-137, por meio do software ProUCL, permitiu avaliar a concentração média do conjunto de dados amostrados. O valor obtido para o terceiro quartil (0,8 Bq kg-1) pode ser utilizado como o valor recomendado mais representativo da radiação de fundo da região. / The Cananéia-Iguape Estuarine-Lagunar Complex, located in the south of the State of São Paulo, Brazil, is a protected area recognized by UNESCO as part of the Biosphere Reserve, due to its importance as a natural ecosystem. This region underwent important changes due to the opening of the Valo Grande Channel, connecting the Ribeira de Iguape river to the Complex, causing contaminants to enter the ecosystem. In order to deepen the studies of this ecosystem, a Research Project entitled \"Environmental study of coastal systems exposed to important anthropogenic actions in the southeast region by means of biogeochemical tools\" was approved. This project aimed to use biogeochemical tools in the study of coastal systems stressed by anthropic influences such as land use for urbanization purposes, agriculture, industrial activities, renovation/installation of port structures and coastal shelf exploitation, keeping in mind, the recommendations given for the preservation and management necessary in the coastal areas. Within the scope of this project, the present work aimed to determine the concentration of the natural radionuclides Ra-226, Pb-210, Ra-228, K-40 and artificial Cs-137 in 34 samples of surface sediments collected in the Cananéia-Iguape Estuarine-Lagunar Complex. The samples were measured by gamma spectrometry using a Germanium Hyperpure - HPGe detector. The mean concentration values obtained in the surface sediments for Ra-226 were 14.2 &plusmn; 8.7 Bq kg-1; for Pb-210 was 31.1 &plusmn; 30.4 Bq kg-1; for Ra-228 of 19.2 &plusmn; 14.9 Bq kg-1 and for the K-40 318 &plusmn; 119 Bq kg-1. The results indicated that there is no anthropogenic contamination and that these values can be considered as the base line of the region. However, the results obtained for the relative standard deviation presented high values, indicating a large dispersion of the results around the mean value. This large dispersion is mainly due to the physical and chemical characteristics of the ecosystems where the sediments were sampled. The Principal Component Analysis obtained from the Pearson correlation matrix showed that in most of the sampling points, the radionuclides are predominantly present in the clay + silt portion and aggregated to the organic matter. Within this set of sampling points, it was possible to visualize three outliers, the sampling point MY3 that presented a more positive correlation with the Ra-226 and Ra-228 concentrations and the Pedra do Tombo and R6 sampling points that presented the highest correlation with the clay + silt and organic matter fraction. The other set of sampling points presented a positive correlation with sand, which indicates a hydrodynamic pattern strongly influenced by the currents generated by the tidal oscillations and by the salinity of the water in these locations. The highest concentration of radionuclides found in the Pedra do Tombo sampling point is due to the fact that this location presents high levels of pelitic sediments, alternation of energy flow, with changes in the direction and intensity of the water flow, allowing the deposition of fine sediments. Moreover, is this location the channel presents a narrowing, which hinders the flow of the fine fraction that ends up accumulating, facilitating the deposition of radionuclides. The results for Cs-137 ranged from <0.5 to 3.2 Bq kg-1. From the results obtained for the concentration of Cs-137 in the 34 samples analyzed, 93% are below the minimum detectable concentration. The statistical analysis of the results obtained for the Cs-137, using the software ProUCL, allowed to evaluate the average concentration of the sampled data set. The value obtained for the third quartile (0.8 Bq kg-1) can be used as the recommended value most representative of the background radiation of the region for Cs.

Metals and radionuclides are environmentally relevant contaminants, yet their potential impacts on marine organisms have not been adequately evaluated. This is especially true for exposures of longer duration and/or lower contaminant concentration (i.e. chronic) which are often more representative of real world scenarios. In this context, a suite of biomarkers at different levels of biological organisation were investigated in an ecologically relevant bivalve species, Mytilus galloprovin- cialis after exposure to nickel (a metal), zinc pyrithione (an organometal) and tritiated water (a radionuclide). These contaminants were chosen based on their differing properties, and hence, mechanisms of action. All three contaminants produced genotoxicity (DNA strand breaks, as measured by the comet assay, and induction of micronuclei [MN]). For nickel (> 1800 µg L −1 ) and tritiated water (15 MBq L−1 ), biomarkers at lower levels of biological organisation (i.e. DNA strand breaks, MN, changes in the expression of key stress response genes) were more sensitive than those at higher levels (i.e. clearance rate, attachment, tolerance of anoxia). In particular, exposure to tritiated water for 14 days resulted in DNA damage and molecular alterations without affecting higher level responses. As environmental contaminants could interact with other physical or chemical stressors in a complex environment, further exploration of biological responses revealed modulation by hyperthermia with concomitant changes in the transcriptional ex- pression of key defence genes (hsp70, hsp90, mt20, p53 and rad51). In contrast to nickel and tritiated water, exposure to both 0.2 and 2.0 µM zinc pyrithione caused significant deviation from concurrent controls for every biomarker examined, suggesting that further investigation of the environmental impacts of this contaminant is particularly necessary. Variation in biological responses induced by different contaminants suggests that potential links between levels of organisa- tion should be evaluated on a contaminant-specific basis. The integrated, multiple biomarker approach used in the current study provides a robust methodology for such studies, which could be translated to other ecologically relevant species for proper evaluation of risks to both environmental and human health.

L’érosion des sols est intense dans les petits bassins versants montagneux en climat tropical. Lorsqu’ils atteignent les rivières, ces sédiments posent divers problèmes à l’aval. L’identification des sources de sédiments et la compréhension de leur dynamique au sein des bassins versants est donc cruciale pour proposer des mesures de lutte efficaces contre ces problèmes. Cette thèse vise à tester et à développer des méthodes de traçage qui consistent à comparer les propriétés physico-chimiques des sols à celles des sédiments transportés dans les rivières pour en définir les sources et pour en contraindre les temps de transfert. Le site d’étude est un bassin de 22,4 km² au Laos équipé d’un emboîtement de stations de suivi et soumis à un régime de mousson. Trois campagnes de prélèvements ont permis de collecter des échantillons de sols de surface, de ravines et de berges ainsi que des eaux de pluies, de ruissellement et de rivières, les matières en suspension (MES) associées et des laisses, au cours de 3 crues de début de mousson en mai 2012 et juin 2013. Les échantillons ont été analysés afin de déterminer leurs activités en radionucléides apportés au sol par les pluies de manière ponctuelle (¹³⁷Cs) ou continue (⁷Be, ²¹ºPb), la teneur et la composition de la matière organique (C organique, N, C/N, δ¹³C et δ¹⁵N), la granulométrie des MES et la composition de l’eau (conductivité électrique, δ¹⁸O). Plusieurs expériences méthodologiques ont permis de tester et valider les hypothèses qui sous-tendent l’utilisation du marquage en ⁷Be et en excès de ²¹ºPb des sédiments (adsorption rapide sur les particules de sol, rapport ⁷Be / ²¹ºPbxs des particules transportées par le ruissellement comparable à celui de la pluie correspondante). Durant la crue de mai 2012, la contribution des sédiments récemment érodés est élevée en début d’événement (25-35%), mais elle est ensuite diluée par la remobilisation de particules déposées sur le lit du cours d’eau ou stockées dans les zones de dépôt. La caractérisation combinée du carbone organique particulaire (COP) et de l’activité en ¹³⁷Cs des particules a mis en évidence la prédominance de l’érosion des sols de surface marqués par leur signature C₃ à l’amont, et l’augmentation de la contribution de l’érosion des berges (marquage C₄) dans la partie aval du bassin. Les valeurs les plus élevées des taux d’exportation de sédiments (43,3 Mg km-2) et de C (0,83 MgC km-2), du coefficient de ruissellement (11,7%) et du pourcentage d’eau de ruissellement dans l’écoulement total (78-100%) ont été observées au niveau de la station drainant en grande partie des versants sous teck. Les teneurs en C mesurées et les flux de COP calculés ici sont beaucoup plus élevés que ceux qui ont été estimés lors de travaux réalisés il y a 10 ans dans le même bassin versant, lorsque la surface couverte de teck y était beaucoup plus faible (2,5% en 2002-2003 contre 32% en 2012). Ainsi, à l’aval, le taux d’exportation spécifique de C lors d’une seule crue en 2012 s’est révélé être 2,6 fois plus important que celui observé au cours de l’année hydrologique 2002-2003 (34 crues érosives). Lors des deux crues de juin 2013, la variabilité spatio-temporelle des retombées de ⁷Be et ²¹ºPb a pu être quantifiée. Ces résultats indiquent qu’il est indispensable de mesurer le signal d’entrée du marquage ⁷Be /²¹ºPb de chaque événement et qu’il est préférable de réaliser un échantillonnage en plusieurs points du bassin plutôt que de le fractionner en un seul point au cours du temps. Durant ces crues, la composition des sédiments a pu être étudiée le long d’un continuum de dix stations emboitées (0,1 ha à 19,8 km²). Les contributions respectives des différentes sources de sédiments, et leur propagation à travers le bassin, ont pu être déterminées à l’aide des mêmes traceurs que lors de la crue de mai 2012. À l’avenir, la combinaison de traceurs proposée dans cette thèse pourrait être appliquée à d’autres évènements ou d’autres sites. / Soil erosion is particularly intense in small mountainous tropical catchments. When supplied to the rivers, eroded sediment leads to numerous problems downstream (transfer of pollutants, increase of water turbidity, dam siltation…). Identifying sediment sources and understanding their dynamics across catchments constitutes a prerequisite to design and implement efficient measures to reduce these problems. This thesis aimed at testing and developing fingerprinting methods, by comparing physico-chemical properties of soils and riverine suspended sediment to define their origin and constrain their transfer across catchments. The study site is a 22.4 km² catchment in northern Laos equipped with nested monitoring stations and submitted to monsoon rainfalls. Three field campaigns were conducted to collect samples of surface soils, gullies, riverbanks, and rainwater, overland flow, river water, suspended matter and deposited sediment during three floods at the beginning of the monsoon in May 2012 and June 2013. Collected samples were analysed to determine fallout radionuclide activities (¹³⁷Cs, ⁷Be and ²¹ºPb), organic matter composition (organic carbon and nitrogen concentrations, C/N ratio, δ¹³C et δ¹⁵N), particle size distribution and water composition (electric conductivity and δ¹⁸O). Several methodological experiments were performed to check assumptions underlying the use of atmospheric 7Be and ²¹ºPb as tracers of sediment (quick adsorption of rainwater radionuclides to soil particles; similarity between /210Pbxs activity ratio measured in overland flow particles and corresponding rainfall signature). During the flood studied in May 2012, the contribution of recently eroded sediment was high at the beginning of the rising stage (25-35%), but was then diluted by sediment remobilization from the riverbed and deposition areas (swamps). The combined determination of particulate organic carbon (POC) and ¹³⁷Cs activity of sediment indicated the dominance of surface soil ( C₃ vegetation labelling) erosion in upstream parts and the increase of riverbank (labelled by C₄ plants) erosion contribution in the downstream part of the catchment. The highest runoff coefficient (11.7%), sediment specific yield (43.3 Mg km-2), total organic carbon specific yield (0.83 MgC km-2) and overland flow contribution (78–100%) were found at the station draining mainly the areas covered with teak plantations. Total organic carbon concentrations and POC specific yields calculated during this thesis are much higher than those obtained during a previous study carried out 10 years earlier in the same catchment, when teak plantations covered a much lower proportion of its area (2.5% in 2002-2003 vs 32% in 2012). At the downstream station, carbon specific yields for the studied flood in 2012 were twice higher than the annual ones observed in 2002-2003 (34 erosive events). During the two floods analysed in June 2013, the spatial and temporal variability of ⁷Be and ²¹ºPb wet deposition was investigated and quantified. The results indicate that the input signal of ⁷Be/²¹ºPb labelling associated with each storm should be determined and that spatially distributed collection of rainfall should be privileged to the sequential time-fractionated sampling at a single location. During these floods, the composition of exported suspended sediment could be studied along a continuum of ten nested stations draining areas between 0.1 ha and 19.8 km². Respective contributions of the different surface and subsurface sources of sediment and their propagation across the catchment, were successfully determined with the same tracers as during the May 2012 event. In future, the panel of parameters used in this thesis could be applied to characterise suspended matter behaviour during floods occurring later in the rainy season, or along a longer continuum of nested monitoring stations.

Este trabalho objetivou estudar a possibilidade de se utilizar líquen como bioindicador de poluição atmosférica para regiões impactadas por radionuclídeos, metais e elementos terras raras. Foram escolhidas como áreas de estudo a região de Pirapora do Bom Jesus, onde se localiza uma indústria de produção de estanho e chumbo metálicos e a região de Cubatão, onde se localiza o complexo industrial de produção de fertilizantes fosfatados. As duas instalações escolhidas são consideradas como indústrias TENORM - Technologically Enhanced Naturally Occurring Radioactive Material, pois podem ocasionar um aumento significativo na concentração dos radionuclídeos naturais nas várias etapas do processo industrial, ocasionando um aumento potencial de exposição à radiação natural em produtos, subprodutos e resíduos gerados. Para tanto foram analisados os radionuclídeos 238U, 226Ra, 210Pb, 232Th e 228Ra, os elementos terras raras e metais em amostras de matéria prima e resíduo das instalações, liquens e solos na área de influência. As amostras de líquen e solo foram analisadas para a determinação de urânio, tório, elementos terras raras e metais por análise por ativação com nêutrons. Os radionuclídeos 226Ra, 228Ra e 210Pb em amostras de solo foram determinados por espectrometria gama, e em amostras de liquens por separação radioquímica e contagem alfa e beta total em contador proporcional de fluxo de gás constante. As concentrações de 238U (de 19 a 473 Bq kg-1), 226Ra (de 21 a 265 Bq kg-1), 210Pb (de 401 a 1461 Bq kg-1), 232Th (de 15 a 574 Bq kg-1), 228Ra (de 176 a 535 Bq kg-1), elementos terras raras, Hf e Ta determinadas nas amostras de liquens ao redor da indústria de produção de estanho e chumbo metálicos mostram que todos estes elementos se concentram significativamente e, portanto, os liquens fornecem uma assinatura da contaminação atmosférica. Os resultados obtidos nas amostras de liquens da região de Cubatão mostram uma assinatura mais evidente do radionuclídeo 210Pb, proveniente de todo parque industrial da região. Os resultados obtidos no presente estudo mostraram que os liquens podem ser usados como bioindicadores de poluição atmosférica por radionuclídeos e elementos traço. / The main aim of this thesis is to study the possibility of using lichen as bioincicator of atmospheric pollution in regions contaminated by radionuclides, metals and rare earth elements. Two regions were chosen, one in Pirapora do Bom Jesus, where a tin and lead industry is located, and a second one in Cubatão, where a phosphate fertilizer industrial complex is located. The two industries chosen are considered as TENORM - Technologically Enhanced Naturally Occurring Radioactive Material, since they can cause a significant increase in the natural radionuclides concentration in the industrial process, and consequently a potential increase in the radiation exposure in products, byproducts and residue. To achieve this aim, the radionuclides 238U, 226Ra, 210Pb, 232Th and 228Ra, rare earth elements and metals were analyzed in samples of raw material an residue from the installations, lichens and soils. Lichens and soil samples were analyzed by instrumental neutron activation analysis for the determination of uranium, thorium, rare earth elements and metals. The radionuclides 226Ra, 228Ra and 210Pb in soil samples were determined by gamma spectrometry and in lichen sample by radiochemical separation and gross alpha and beta counting on a gas flow proportional counter. The concentrations of 238U (from 19 to 473 Bq kg-1), 226Ra (from 21 to 265 Bq kg-1), 210Pb (from 401 to 1461 Bq kg-1), 232Th (from 15 to 574 Bq kg-1), 228Ra (from 176 to 535 Bq kg-1), rare earth elements, Hf and Ta determined in lichen samples around the tin and lead industry show an enrichment in these elements. Therefore, the lichens can be used as a fingerprint of the atmospheric contamination. The results obtained for the lichen samples, in the Cubatão region, present a fingerprint mainly of 210Pb, from industries of the region. The results obtained in this study showed that the lichens can be used as bioindicators of atmospheric pollution by radionuclides and trace elements.